Cold Weather Makes Snow Squeak: The Science Behind It

[AEM]

Right now it's a bit chilly in the upper midwest (-21 degrees this morning at 6:00 am; -23 degrees predicted for tonight). When walking our dog this afternoon, my wife and I noticed that the snow underfoot squeaked louder that usual. We observe that snow makes a qualitatively different sound depending on temperature with the most noticeable squeaking starting at about -10 degrees. (All degrees in this post are Farenheit.) Why should the sound made when walking on snow depend on temperature, and why should it appear louder the lower temperature?

 

[mgb_phys]

Everything you ever wanted to know about snow
http://nsidc.colorado.edu/snow/faq.html

Why does snow crunch when you step on it?
At what temperature does it crunch?

A layer of snow is made up of ice grains with air in between the ice grains. Because the snow layer is mostly empty air space, when you step on a layer of snow you compress that layer a little or a lot, depending on how old the snow is. As the snow compresses, the ice grains rub against each other. This creates friction or resistance; the colder the temperature, the greater the friction between the grains of ice. The sudden squashing of the snow at lower temperatures produces the familiar creaking or crunching sound. At warmer temperatures, closer to melting, this friction is reduced to the point where the sliding of the grains against each other produces little or no noise. It's difficult to say at what temperature the snow starts to crunch, but the colder the snow, the louder the crunch.

 

[PhanthomJay]

Right now it's a bit chilly in the upper midwest (-21 degrees this morning at 6:00 am; -23 degrees predicted for tonight). When walking our dog this afternoon, my wife and I noticed that the snow underfoot squeaked louder that usual. We observe that snow makes a qualitatively different sound depending on temperature with the most noticeable squeaking starting at about -10 degrees. (All degrees in this post are Farenheit.) Why should the sound made when walking on snow depend on temperature, and why should it appear louder the lower temperature?

I suppose this site offers as good an explanation I can find:
http://cimss.ssec.wisc.edu/wxwise/squeak.html

Apparently, at the colder temps, the water in the snow freezes, and thus becomes a dry (i.e, water in its frozen state) snow, causing crushing of the ice crystals , and hence, more noise as you walk on it; also, the sound is not absorbed as well as a fresh fallen snow, so the sound is louder. I've noticed, however, that when the temperature is around 20 to 30 degrees or more, degrees F, the snow is relatively quiet when you walk on it; in the 0 to 20 degree range, degrees F, you get a "crunch,crunch" sound; and when the temperature drops below zero, you get that "squeak, squeak" sound. I'll check it out tomorrow morning when the temperature is expected to drop to 5 below in these parts. Interesting!

 

[AEM]

Thanks for the feedback and links. My wife (who is an applied mathematician) and I had surmised the answer, but it's nice to have confirmation. Stay warm!

 

[Andy Resnick]

Interesting links. I also know that different ski wax formulations are used for different temperatures- don't know any real details, other than they are different colors.